Add Subtract Equalize

Chef has an array $A$ of length $N$. In one operation, Chef can do the following: - Select any non-empty subsequence $S = \{S_1, S_2, S_3, \ldots S_k\}$ of $A$ (where the $S_i$ are the **indices** of the array representing the chosen subsequence) - Then, choose one index from this subsequence, say $S_j$ - Finally, either add $A_{S_j}$ to every element of the subsequence, or subtract $A_{S_j}$ fr